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bpo-34164: Fix handling of incorrect padding in base64.b32decode(). (GH-8351)

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Now base64.Error is always raised instead of UnboundLocalError or
OverflowError.
This commit is contained in:
Serhiy Storchaka 2018-07-24 12:52:51 +03:00 committed by GitHub
parent 02ec92fa7b
commit ac0b3c2f4d
No known key found for this signature in database
GPG Key ID: 4AEE18F83AFDEB23
3 changed files with 21 additions and 17 deletions
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17
Lib/base64.py
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@ -231,23 +231,16 @@ def b32decode(s, casefold=False, map01=None):
raise binascii.Error('Non-base32 digit found') from None
decoded += acc.to_bytes(5, 'big')
# Process the last, partial quanta
if padchars:
if l % 8 or padchars not in {0, 1, 3, 4, 6}:
raise binascii.Error('Incorrect padding')
if padchars and decoded:
acc <<= 5 * padchars
last = acc.to_bytes(5, 'big')
if padchars == 1:
decoded[-5:] = last[:-1]
elif padchars == 3:
decoded[-5:] = last[:-2]
elif padchars == 4:
decoded[-5:] = last[:-3]
elif padchars == 6:
decoded[-5:] = last[:-4]
else:
raise binascii.Error('Incorrect padding')
leftover = (43 - 5 * padchars) // 8 # 1: 4, 3: 3, 4: 2, 6: 1
decoded[-5:] = last[:leftover]
return bytes(decoded)
# RFC 3548, Base 16 Alphabet specifies uppercase, but hexlify() returns
# lowercase. The RFC also recommends against accepting input case
# insensitively.

19
Lib/test/test_base64.py
View File

@ -343,11 +343,20 @@ class BaseXYTestCase(unittest.TestCase):
self.assertRaises(binascii.Error, base64.b32decode, data_str)
def test_b32decode_error(self):
for data in [b'abc', b'ABCDEF==', b'==ABCDEF']:
with self.assertRaises(binascii.Error):
base64.b32decode(data)
with self.assertRaises(binascii.Error):
base64.b32decode(data.decode('ascii'))
tests = [b'abc', b'ABCDEF==', b'==ABCDEF']
prefixes = [b'M', b'ME', b'MFRA', b'MFRGG', b'MFRGGZA', b'MFRGGZDF']
for i in range(0, 17):
if i:
tests.append(b'='*i)
for prefix in prefixes:
if len(prefix) + i != 8:
tests.append(prefix + b'='*i)
for data in tests:
with self.subTest(data=data):
with self.assertRaises(binascii.Error):
base64.b32decode(data)
with self.assertRaises(binascii.Error):
base64.b32decode(data.decode('ascii'))
def test_b16encode(self):
eq = self.assertEqual

2
Misc/NEWS.d/next/Library/2018-07-20-18-06-00.bpo-34164.fNfT-q.rst Normal file
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@ -0,0 +1,2 @@
:func:`base64.b32decode` could raise UnboundLocalError or OverflowError for
incorrect padding. Now it always raises :exc:`base64.Error` in these cases.